fix: use correct flatpak action repo again, after it moving twice

Author: Totto16

.github/workflows/flatpak.yml

@@ -28,7 +28,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - uses: flathub-infra/flatpak-github-actions/flatpak-builder@9386d85446c0f8c6b93dea3774002af2abcac3d5
+      - uses: flatpak/flatpak-github-actions/flatpak-builder@v6
         with:
           bundle: oopetris.flatpak
           manifest-path: io.github.openbrickprotocolfoundation.oopetris.yml